I didn't think anyone would actually build one !
Now you need a way to do the arctan function in hardware. Or, thinking
laterally, a servo loop off the Q channel driving a phase shifter.
I'll put out another transmission during the week sometime. Monday is not
possible as I go off to my Camera Club then, but lets say provisionally
From: James Moritz <[email protected]>
To: [email protected] <[email protected]>
Date: 16 February 2002 16:37
Subject: LF: Re: G4JNT "PSK CW" transmission/ Phase display
Dear Andy, LF group,
I had a few problems with corrupted downloads of Wolf's SpecLab software,
so was not able to use it to decode G4JNT's PSK signal last night -
however, it was easy to copy the "G4JNT PSK CW"message using the phase
transitions visible on the spectrogram as before.
While I was hanging around, I thought it would be fun to follow Andy's
suggestion and build a breadboard hardware vector display to use with an
oscilloscope - unfortunately, Andy had gone QRT by the time it was working,
but it was certainly interesting to look at other LF signals in this way.
The phase jumps on DCF39 are clearly seen. With a wider bandwidth, you can
observe the phase modulation on the Radio 4 198kHz signal. The French
station on 162kHz has something similar, but with rather greater phase
deviation. Atlantic 252 is a couple of Hz low in frequency, and the phase
has a funny little wobble. GBR on 15.98kHz is particularly intriguing and
quite hypnotic - the phase of the MSK signal is changing all the time, the
symbols appear to be represented by changes in the direction of the phase
shift from increasing to decreasing or vice-versa, which occur at fixed
points on the phase circle. I'll definitely have to build it up more
Cheers, Jim Moritz
73 de M0BMU